Presently, there are a wide variety of projection technologies available in the marketplace. For example, overhead projectors, front projection televisions and rear projection televisions each employ projector technologies. Current projection systems frequently employ a high-output arc lamp to provide as an illumination source. Arc lamps are known to generate significant levels of waste heat while operating, producing surface temperature differentials of several hundred degrees Fahrenheit on various portions of the lamp. Additionally, a lamp housing that typically encloses such a lamp can also reach temperatures of many hundred degrees during operation of the lamp. Consequently, most projection systems incorporate a fan to provide forced convective cooling of the arc lamp and the lamp housing. However, the significant temperatures involved frequently require that the fan continue to run for a period of time after the lamp has been de-energized in order to dissipate heat retained in the lamp and lamp housing, both to preserve the lamp and to protect other parts of the projection system from thermal stress.
Clearly, the need to provide forced-air convective cooling of the lamp and its assembly after the lamp has been de-energized will mandate that the projection system then continue to provide electrical power to the fan motor. However, if power to a projection system is interrupted by a power outage or a tripped circuit breaker, or by someone inadvertently pulling the power cord from a line power socket, damage to the projection system due to excessive heat build up is possible. Furthermore, operation of the fan often significantly increases the ambient noise level, which is very apparent and undesirable when the projection system is used in a quiet environment. Therefore, a projection system that allows instant interruption of electrical power without risking thermal damage to the lamp or other components of the projector system would be of particular interest.